1. Field of the Invention
The present invention concerns a movable selector element mounted within an electrical apparatus comprising a series of voltage outputs connected to an electrical step transformer. In such apparatus, the movable contacts of the selector element cooperate with fixed contacts connected to the voltage outputs.
2. Related Art
The European patent No. 0029467 describes a movable selecting linkage consisting of one central and two end yokes. In this patent, the central yoke is telescopic and carries the principal movable contacts. Each end yoke swivels and supports the auxiliary movable contacts. The main and auxiliary movable contacts are in the form of rollers located alone or in parallel between the two arms of their respective yoke. For the swiveling yokes, the continuity of the electric circuit between the elements driven into relative motion is provided in conventional manner by elastic rings made of a good electrical conducting material.
In such an assembly, the number of stacked elastic rings varies as a function of the mechanical loading to be applied. However, considering the dimensional deviations occurring in assembly, it is often difficult in practice to maintain the intended mechanical loading. Inadequate loading results in microwelds from electric arcing. Excessive loading leads to premature wear and even to shearing the corrugated ring with attending danger of large damages to the apparatus from debris dispersion. On the other hand, the use of this technique to assure the continuity of the electric circuit between the swiveling yoke and the voltage output is delicate because, depending on the mechanical loading of the elastic disks made of an good electrical conducting material, the yoke motion may be slowed down and thereby affect the sharpness of the break of the auxiliary contacts.